As far as DRM-Free games go, GOG obviously. But also Shinyloot.com and Desura.com mostly provide drm-free versions of games (unless stated).

Bundle-wise, aside from Humble, Groupees really is one of the only sites to really provide DRM-Free titles, you do need to check though before buying as the DRM-Free isn't always there

Shinyloot unfortunately follows a concept I simply cannot agree with:
ShinyLoot has a unique take when it comes to DRM. Steam requires Steam (duh!), GOG is all DRM-free, and most other stores sell mainly Steam keys. We prefer the most minimal amount of DRM when possible, offering over 80% of our library DRM-free. However, there are some games that do require Steam and we feel that it's important to support those games too. We're first and foremost about game discovery and exploration so selling Steam required games means you get better results!
So, while it would be okay for me to check every game for DRM, Steam and so on, I do not want to support such ideas.

Groupees looks nice, they have GOG.com keys and offer most games DRM-free, as far as I can tell, but I heard a few negative opinions about them, including bad support.

Actually, the inclusion of games that come only in the form of a Steam key is very recent and was discussed both here and on their own forums (I could find the links, if you're interested). The positive thing about ShinyLoot is that they're also actually listening and taking feedback seriously. This resulted to them committing to always maintain the ratio of DRM-free/ DRM-lite (that's a one time activation key) games to Steam ones at 85/15.

One thing that ShinlyLoot does really well, is the search filters - you can select to only be served truly 100% DRM-free games.

But from your OP, I knew you would object ShinyLoot, that's why I didn't suggest them in my first post.